Non-magnetic, explosive actuated indexing device



July 18, 1967 J. P. BAUERNSCHUB, JR 3,331,255

lNON-MAGNETIC, EXPLOSIVE ACTUATED INDEXING DEVICE Filed OC'C. 7, 1965 3 Sheets-Sheet l INVENTOR John P. auernschub, Jr.

'TTORNEYS Fig.

SENSOR [58 POS! TON IND/CA TOI? July 18, 1967 J.P. BAUERNSCHUB, JR 3,331,255

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United States Patent O ABSTRACT F THE DISCLOSURE An indexing device with positionable means having at least first and second stable positions, a ratchet arm, a ratchet coupled to the positionable means and engageable with the ratchet for retaining the positionable means in one stable position, and explosive means for actuating the ratchet arm to momentarily release the ratchet and permit the positionable means to assume another stable position.

The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

This invention relates to a non-magnetic indexing device and more specifically to an apparatus and method for orienting a magnetic flux Isensing instrument in a magnetic iield ywithout the generation of detrimental magnetic fields.

A conventional method for indexing a shaft (and any apparatus or device coupled to the shaft) is through the actuation of the stepper motor or a solenoid actuated devi-ce.

The actuation of the motor or the solenoid requires a ow of current and it is well known that parts of these devices must be magnetic and that a magnetic field is formed about current carrying conductors or elements. In many applications, the generation of the magnetic eld due to the current flow through an actuating device produces no harmful effects and is rarely taken into consideration. In other environments and applica. tions, the magnetic fie-ld `so generated can be tolerated only to a degree so that certain types of shielding may be satisfactory in reducing the intensity of the field to a tolerable level. However, since a magnetic iield exists in space about the earth, and perhaps about other planets and celestial bodies, the measurement of the intensity, direction, etc. of these magnetic fields is a natural exercise of mans eternal quest for knowledge.

The magnetic field intensity about the earth and other bodies is very small. Accordingly, if this field is to be measured, the measuring instrument must be highly sensitive and one must be a-ble to selectively position the instrument for calibration purposes. In certain types of magnetometers, the accepted manner for deriving absolute values of the magnetic fields is through a reversal of the axis of the measuring instrument. For example, values are recorded with the instrument in a first position and are again recorded with the instrument in a second position, substantially 180 removed from the first position.

It will be intuitively clear that if la minute magnetic field is to be measured by a highly sensitive instrument, and, further, that the instrument must be rotated upon its axis at certain intervals, then the conventional means of stepping motors or solenoid actuated devices cannot be employed since each of these devices have a magnetic field that cannot be tolerated by the magnetic ux sensing instrument. Understanda-bly, if conventional means were employed to orient the sensing instrument, then the values of the magnetic field intensity or direction recorded would ICC be of little value since one would not know whether the recorded value included the measurement of the desired field o1' the measurement of the desired field including a spuriously generated `and unwanted field.

In the present invention, the apparatus for orienting or indexing the magnetic flux sensor is actuated through the detonation of a small explosive charge which is nonmagnetic by nature and has no magnetic influence upon the magnetic flux sensing instrument.

Accordingly, it is the principal object of the ypresent invention Ato improve indexing or shaft orientation apparatus.

It is a further object of the present invention to improve indexing apparatus of the non-magnetic type.

It is a further object of the present invention to provide ,an instrument indexing apparatus which employs the force created through the detonation of an explosive char-ge to index the apparatus.

It is a further object of the present invention to provide a magnetometer positioning device of the non-magnetic type for Calibrating absolute values of magnetic fields.

It is a further object of the present invention to provide an instrument indexing apparatus employing explosive actuators ywhich may be repeatedly indexed to successive positions to again index the apparatus.

It is a further object of the present invention to provide an instrument indexing apparatus employing explosive actuators which are removed and replenished after each detonation so as to repeatedly index the apparatus to successive positions.

It is a still further object of the present invention to provide a mechanism for supplying precision rotary motion on command for a system requiring only a limited number of operations and Where electrical power is limited.

These and other objects of the present invention are accomplished by an indexing apparatus wherein the magnetic ux sensing instrument along with an electrical cable container are positioned upon a rotatable shaft. A ratchet is secured to the shaft and the shaft, being biased for rotation in one direction, is arrested in one of two positions through the engagement of the ratchet with a ratchet arm. Each of the two positions are stable positions `and are located approximately removed from each other.

The foregoing ratchet arm is pivotable and is secured to a second ratchet arm which includes a pair of piston surfaces positioned approximately 180 from each other. Within the contour of the second ratchet arm is a piston actuator housing which supports a plurality of piston actuators about its periphery. A commutator bearing a plurality of electrical conductors is secured to the piston actuator housing. A commutator brush support assembly is rigidly positioned and the brushes of the commutator brush support assembly engage the conductors of the commutator as the commutator, being biased for rotation in a direction opposite to the direction of rotation of the magnetic flux sensor, rotates. The entire assembly is supported, as appropriate, from a main structure and a nonmagnetic cover is positioned over the entire sensing and indexing apparatus.

To rotate the sensing instrument (to index the device), an electrical pulse is transmitted to the apparatus which causes the detonation of a small explosive charge in a piston actuator positioned in a piston actuator housing. The force of the detonation extends a piston about 1/s inch. This piston is directed against one of the piston impact surfaces of the second ratchet arm, causing the ratchet arm to pivot outwardly and carry the first ratchet arm along with it. The ratchet, along with its shaft and magnetic ux sensing instrument, disengages the first ratchet arm, rotates 180, and reengages the first ratchet arm to then halt in its other position.

Simultaneously, the second ratchet arm will permit approximately a rotation of the piston actuator housing and the commutator coupled thereto. In this manner, an undetonated explosive actuator (actually a pair oactuators) is positioned under the opposite piston impact surface of 4the second ratchet arm. During the rotation of the commutator upon detonation of the explosive charges, all explosive charges not selected are shorted out so as to prevent their accidental firing. Since the apparatus of the present invention is designed for use in a space vehicle, the electrical output of the magnetic flux measuring instrument in both of its positions would be transmitted through 4the space vehicles electronic communication system to a ground station. In addition to the sensing instrument output, a signal is also generated in the apparatus for indicating whether the sensing instrument is in its first position or its second position. It will be readily understood by those skilled in the art that, although the apparatus is described with reference to two stable positions of the sensing instrument, it may be readily adapted for many more different rotational positions than the two set forth by the provision of additional stops to the ratchet engaging ratchet arm. In addition, it Will be evident to those skilled in the art that there are other ways of obtaining the same mechanical output from the apparatus. For example, the dual ratchet can be replaced by a single ratchet and a gear train to couple the flux measuring instrument and the piston actuator case. A device incorporating a planetary gear system is also envisioned.

As set forth, one of the particularly salient features Of the invention is the manner in which the explosive devices are incorporated to obtain repeated indexing operations. Normally, such explosive devices are only used for oneshot operations because, by their very nature, they can be tired only once and cannot be retracted. The mechanism of the present invention provides for the removal and the replenishment of the explosive actuator for additional successive cycles.

The invention both as to its organization and method of operation together with further objects and advantages thereof will best be understood by reference to the following specification taken in conjunction with the accompanying drawings in which:

FIGURE 1 is a perspective view of the invention and illustrating the encased magnetic flux sensing instrument to the left, the centrally positioned indexing mechanism, and the boom and mounting flange on the right;

FIGURE 2 is an elevational view of the apparatus, partly in section, and emphasizing lthe piston actuator or explosive charges, and other elements of the invention;

FIGURE 3 is an exploded view of the invention and illustrates the more important elements of the invention while eliminating the showing of such lesser elements as washers, spacers, cable conduits, pins, etc.;

FIGURE 4 is a sectional view taken along the line 4 4 of the FIGURE 2 and showing the piston surfaces bearing ratchet arrn which initiates the indexing operation after detonation and also steps the piston actuator housing;

FIGURE 5 is a view similar to the FIGURE 4 but illustrating the piston actuator ratchet arm in its second stable position;

FIGURE 6 is a sectional view taken along the line 6-6 of the FIGURE 2 and illustrating the ratchet engaged by the rst ratchet arm which yields a first position of the magnetic iiux sensing instrument;

FIGURE 7 is a View similar to the FIGURE 6 except the ratchet and ratchet engaging arm are shown in their other position which produces the second stable position of the sensing instrument which is substantially 180 removed from the first position;

FIGURE 8 is an elevational view of the commutator brush support assembly and illustrating the position of the various brushes of the assembly;

FIGURE 9 is an elevational view of the commutator which is engaged by the commutator brush support assembly ofthe FIGURE 8;

FIGURE 10 is a diagrammatic electrical schematic illustrating the manner in which the explosive charges or piston actuators are fired or, if not selected for detonation, retained at ground potential so as to eliminate any possibility of accidental tiring;

FIGURE 11 is an electrical schematic illustrating the manner in which the position of the magnetic ux sensing instrument is determined; and

FIGURE 12 is a fragmentary view, partly in section, illustrating the position, in dotted outline, of a piston actuator prior to detonation and the position -of the piston, in solid outline, after detonation and driving the piston impact surface of the piston ratchet arm outwardly.

Initial reference will be had to the FIGURES 1, 2 and 3. The FIGURES 1 and 2 illustrate the assembled position of the various elements of t-he indexing device while the FIGURE 3, being an exploded view of the device, succinctly illustrates the configuration of the various elements in their unassembled form.

In order that the invention not be obscured, a number of the minor elements such as spacers, clamps, cable conduits, etc. have been omitted from the exploded view of the -FIGURE 3.

With reference to the FIGURES 1, 2 and 3, the indexing apparatus is supported upon a boom 14 which Vis mounted in and secured to a mounting flange 16. The mounting ange 16 has a reduced circular portion 18 which receives the boom 14 and is secured thereto by any suitable means. An aperture 20 is centrally positioned along the axis of the mounting flange 16 and receives an electrical connector 22 which connects the electronics of the indexing device with a cable (not shown) communicating with the device through the boom 14.

A main structure 24 of generally circular configuration and having a plurality of apertures, projecting arms, etc. for receiving the various elements of the indexing mechanism, is secured to the mounting flange 16 and aligned with the mounting flange 16 by the bosses 26. The main structure 24 may be secured in any suitable manner to the mounting flange 16 such as by a plurality of bolts 28, one of which is shown in the FIGURE 2. A standoff connector 30 is positioned within the mounting flange 16 at the aperture 20 and engages a pair of bosses 32 and 32'. A cable conduit 34 of generally square U construction is secured to the standoff connector 30 and extends under (according to the position of the device) the indexing apparatus to be hereinafter described, and has its other end supported by a main shaft 36. Substantially all of the lremaining elements are assembled about the main shaft 36.

The main structure 24 includes an annulus 38 which is secured to the mounting flange 16 and three substantially axially parallel arms 40, 42 and 44 extending from the annulus 38 and equidistant from the axis. At the end of the arms 40, 42 and 44 opposite to the annulus 38, three projections 46, 48 and 50 are joined, respectively, to the arms 4t), 42 and 44 and converge toward `an axial ring 52. The axial ring 52 supports an axial sleeve 54, as shown. The standoff connector 39 is supported in the area adjacent the aperture S3 and then to the cable conduit 34, as previously described. Projecting inwardly from each of the arms 40, 42 and 44 are a pair of ears 60 and 62 which are visible while the third ear projects from the arm 44. An aperture is formed in each of the ears 60, 62 and the invisible ear, to receive a bolt 66 (it being understood that there is a bolt received in each of the ears) for securing thereto a commutator brush support assembly 68. The commutator brush support assembly 68 is rigidly secured to the main structure 24 and supports a plurality of bifurcated contacts, only four of which are shown in the FIGURE 3, whose function and operation will be set forth with reference to the FIGURES 8 and 9. A pair of contacts 70 and 72 are illustrated in the FIG- URE 2 for reference purposes. The commutator brush support assembly 68 is of a non-conductive or insulating material so as to provide insulation between certain of the contacts.

One end of the shaft 36 is suitably supported within the centrally positioned aperture of the brush support assembly 68, and an eccentrically mounted pin 74, secured to the shaft 36 extends through the brush assembly 68 and alternatively engages a pair of switch arms 76 and 78 projecting from, respectively, a pair of sensor position indicating switches 80 and 82, only the switch 80 being visible in the FIGURE 2. The operation of the switches 80 and 82 will be discussed with subsequent reference to the FIGURE 11.

Continuing leftwardly from the rightward end of the shaft 36 adjacent the eccentrically mounted pin 74, a piston actuator housing 84 having an axial sleeve 86 is loosely mounted upon the shaft 36 and has a commutator 88 positioned about the axial sleeve 86 and secured to a face of the piston actuator housing 84. The contacts 70, 72, and the remaining contacts of the commutator brush support assembly 68 engage the conduct-ors printed upon the face of the commutator 88, the commutator 88 being discussed with reference to the FIGURE 9. Secured to the opposite face of the piston actuator housing 84 is a power spring housing 90 which is loosely mounted over the shaft 36. The power spring housing 90` has a pai-r of ears 92 and 94 extending therefrom which are provided with a plurality of apertures to receive an equal number of pins Ior bolts 96 extending from the face of the piston actuator housing 84. The pins not only secure the power `spring housing l90` to the piston actuator housing 84 but also serve as indexing pins which cooperate with a ratchet arm to reposition the piston actuator housing 84 after each detonation of a piston actuator or explosive charge, to be hereinafter described. A power spring 98 is fitted within the power spring housing 490 and has its outer end 100 secured to a lobe 102 of the power spring housing 90 and its inner end 104 secured to` the shaft 36 at the aperture 106. As viewed in the FIGURE 3, the power spring housing 90, piston actuator housing 84, and commutator 88 are biased for rotation in a clockwise direction while the main shaft 36 is biased for rotation in a countercl-ockwise direction.

The piston actuator housing 84 has a plurality of pairs of peripherally located and axially oriented apertures 108 which are adapted to receive a piston actuator 110, two of which are shown in the FIGURE 3. A piston actuator 110 is positioned in each of the apertures 108 and are arranged in pairs lfor redundancy. This provides lan added .feature of positive indexing in the event of the failure of one of the actuators 110 to detonate and it is very unlikely that two detonators in parallel would both fail to detonate. As a result, indexing of the apparatus upon command, is assured. A piston actuator 110* houses an explosive charge, which upon detonation, drives a small piston outwardly to engage a piston impact surface of a ratchet arm. Subsequent reference will be had to IFIG- URE 12 wherein the actuator 110 and their operation will be fully described.

As best shown in the FIGURE 3, a ratchet or pawl 112 has an aperture 114 which fits about the shaft 36 and is rigidly secured thereto by a roll pin (not shown). The ratchet 112 has a hook 116 formed at its outer end for engaging a irst stop 118 and a second stop 120 formed on a sensor ratchet arm 122. The sensor ratchet Varm 122 is pivoted at 124, and as shown in the FIGURES is such that it has a first off-center position so as to urge the sensor ratchet arm 122 in a clockwise rotational sense to engage the stop 118 and a second off-center position wherein the ratchet 122 is urged in a counterclockwise rotational sense so that the hook 116 of the ratchet 112 will engage the stop 120.

A second ratchet arm is employed in the practice of the invention and is identified as a piston ratchet arm 134 and is also mounted for limited pivotable move-ment upon the ratchet shaft 126. The ratchet shaft 126, extends between the projection 46 and an inwardly directed projection 136 formed from the inner surface of the arm 40. As best shown in FIGURE 2, the shaft 126 passes through the projection 46, a spacer 138, the pivot 124 of the sensor ratchet var-m 122, the projection 136 from the arm 40, and a pivot point 140 of the piston ratchet ar-m 134. The piston ratchet arm 134 has a pair of opposed inwardly directed dogs 142 and 144 which Iare adapted to engage the pins 96 secured to the face of the piston actuator housing 84. A pair of pins 146 and 146 extend from the piston ratchet arm 134 and are equally spaced from the pivot 140. The pins 146 and 146 are adaptedto enter the apertures 56 and 58, respectively, of the sensor ratchet arm 122 and in this m-anner, the piston ratchet arm 134 and the sensor ratchet arm 122 rock as a unit. Adjacent each of the dogs 142 and 144 is a liat surface or piston impact surface 148 and 150, respectively, which alternately engage the piston caused by the detonation of the explosive charge in the piston actuators 110. Through the cooperation of the piston ratchet arm 134, the dogs 142 and 144, and the pins `96 projecting from a face of the piston actuator housing 84, the force of the piston directed agains-t either of the piston impact surface 148 and 150 will cause a type of escapement movement which, due to the unique construction of the ends of the dogs 142 and 144, causes the piston actuator housing 84 to rotate a suliicient amount as to position a new and undetonated set of piston actuators 110 under one of the piston impact surfaces 148 or 150. In an embodiment of the invention which was constructed and operated in accordance with the teachings of the present invention, the rotational movement permitted to the piston actuator housing 84 was 15 and the sets of piston actuators 110 were spaced accordingly. The detonation of the piston actuators 110 proceeds from a set of detonators 110 which may act against the piston impact surface 148 to a second set of piston actuators 110 which are substantially 180 removed from the lirst set of actuators 110 and act against the piston impact surface 150 and then back to a third set, adjacent the first set, which act against the piston impact surface 148,

and so forth. The complete operation of the indexing device will be reserved for discussion in the section on the operation of the device.

The shaft 36 extends through the sleeve S4 of the main structure 24 and is secured to a mounting projection 152 by any suitable means such as the bolts 154. A cable container 156 is formed from the mounting projection 152 land surrounds the sleeve 54 but at a distance suliicient to permit several turns of electrical cable to surround the sleeve 54. A magnetic liux sensor 158 has a mounting flange 160 secured thereto which bears a plurality of Iapertures 162 which mate with apertures in the mounting projection 152 so as to accommodate a plurality of bolts 164. In this manner, the magnetic flux sensor 158 will follow the excursions of the ratchet 112 and the main shaft 36 coupled thereto. The magnetic iiux sensor 158 is oriented in a iirst position and in a second position substantially removed from the first position. Each time the piston actuators are detonated, the magnetic flux sensor 158 seeks its outer position.

Finally.- la cover 166 of a material having suitable nonconducting properties such as fiberglass, is positioned over the entire mechanism and secured by a plurality of peripheral screws 168 which seat in a plurality of apertures 170 formed on the main structure 24.

With reference to the FIGURES 4 and 5, the FIGURE 4 illustrates one of the two positions of the piston ratchet arm 134 while the FIGURE 5 illustrates the other position of the piston ratchet arm 134. The piston ratchet arm 134 oscillates between its two positions and is actuated by the detonation of the piston actuators 110. The piston actuators 118 selected for detonation alternate from one side of the piston actuator housing 84 to the opposite side or approximately 180 removed from the previously iired or detonated piston `actuators 110. After each detonation, the piston ratchet arm 134 moves to its other stable position.

More specifically, as shown in the FIGURE 4, the dog 142 is shown engaging the pin 96a and serves to retain the piston actuator housing 84 in the position shown. It will be recalled that the piston actuator housing 84 is biased in a clockwise direction as viewed in the FIGURE 4. In the position as shown, the piston impact surface 148 (perhaps more appropriately, a piston surface) is resting against a pair of piston actuators 110 (not visible in the FIGURE 4) which are mounted about the periphery of the piston actuator housing 84. When it is desired to rotate or index the magnetic ilux sensor 158, the electronic circuitry will select the piston actuators 110 immediately under the piston impact surface 148 so that the piston ratchet arm 134 will be driven outwardly about the shaft 126 in the direction of the arrow as indicated in the FIGURE 4. The detonation of the selected piston actuators 110 will not only permit approximately of clockwise rotation of the piston actuator housing 84 but will also permit 180 counterclockwise rotation of the shaft 36 upon which the magnetic flux sensor 158 is mounted. The indexing of the magnetic flux sensor 158 will be subsequently discussed with reference to the FIGURES 6 and 7.

In the FIGURE 5, the position of the piston ratchet arm 134 and the piston actuator housing 84 are shown after detonation of the piston actuators 110 against the piston impact surface 148. The operation of the device produces a type of escapement movement in that the dog 142 has released the pin 96a, thus permitting clockwise rotation of the piston actuator housing 84 and as the dog 144 is driven inwardly toward the axis of rotation of the piston actuator housing 84, the dog 144 will engage the pin 96C and thus halt the rotation of the piston actuator housing 84. This operation positions a pair of undetonated piston actuators 110 under the piston impact surface 150. When it is again desired to index the magnetic ux sensor 158, the piston actuators 110 under the piston impact surface 150` would be detonated thus driving the piston ratchet arm 134 about its pivot shaft 126 with the piston ratchet 134 being moved to a position as indicated yby the arrow in the FIGURE 5. The dog 144 will be driven away from its engagement with the pin 96C and the dog 142 will engage the pin 96b and .thus again permit limited rotation of the piston actuator housing 84 so as to position a pair of undetonated piston actuators 110 under the piston impact surface 148. After .the piston actuators 119 under the piston impact surface 150 are detonated, the piston ratchet arm 134 assumes the position shown in the FIGURE 4 except .that the dog 142 is now engaging the pin 96b rather than the pin 96a. In this manner, the piston actuators 110 can be successively fired or detonated until all -actuators 110 have been discharged.

The FIGURES 6 and 7 illustrate .the two positions of the ratchet 112 and consequently the two positions of the magnetic ux sensor 158. Each time the piston ratchet arm 134 oscillates, the sensor ratchet arm 122 also pivots since both are secured by a common shaft 126 to the main structure 24 and are coupled through the pins 146 and 146 to each other. As shown in the FIGURE 6, the stop 118 of the sensor ratchet arm 122 is shown engaging the hook 116 of the ratchet 112. This is a stable position which retains the shaft 36 and the magnetic flux sensor 158 in one of its two positions. It will be recalled that the shaft 36 is biased counterclockwise, as viewed in the FIGURES 6 and 7 by the power spring 98.

When the piston ratchet arm 134 is driven outwardly in the direction indicated by the -arrow of the FIGURE 4, the sensor ratchet arm 122 of the FIGURE 6 is also pivoted outwardly about the shaft 126 causing the stop 118 .to disengage the hook 116 of the ratchet 112. This pivoting of the sensor ratchet arm 122 now positions the stop 120 in the path of the hook 116 so that the ratchet 112 is halted as shown in the FIGURE 7 when the hook 116 engages the stop 120. Since the magnetic flux sensor 158 is coupled to the shaft 36, the sensor 158 h-as been rotated approximately 180. It will `be recalled that the ratchet 112 is biased counterclockwise as viewed in the FIGURES 6 and 7 due to the power spring 98, both of which are connected to the shaft 36.

When it is again desired to rotate the magnetic ux sensor 158, the piston actuators under the piston impact surface of the FIGURE 5 will be detonated so as to pivot both the piston ratchet arm 134 and the sensor ratchet arm 122 about the shaft 126 and cause the stop 120 to disengage the hook 116. As the sensor ratchet arm 122 pivots outwardly in the direction of the arrow shown in the FIGURE 7, the st-op 118 will be positioned in the path of the hook 116 so that engagement of the hook 116 and the stop 118 takes place. Again, the magnetic flux sensor 158 has been rotated 180 or back to its original position as determined by the position of the elements illustrated in the FIGURES 4 and 6. The ratchet spring 128, best illustrated in the FIGURE 1, assists in maintaining the sensor ratchet arm 122 and the piston ratchet arm 134 in each of their positions as shown in the FIGURES 4 through 7.

The commutator brush support assembly 68 of the FIGURE 8 and the commutator 88 of the FIGURE 9 serve to supply firing current to .the selected piston actuators 110; to short out the non-selected piston actuators 110; and, to provide a signal indicating whether the zero degree side or the side of the piston actuator housing 84 is in tiring position. The commutator brush support assembly 68 is maintained stationary with respect to the main structure 24 by being bolted thereto by the bolts 66 which extend from a plurality of ears 172, 174 and 176 equally spaced about the periphery of the support assembly 68. On the other hand, the commutator 88 rotates along with the piston actuator housing 84 since it is secured thereto so that the contacts, to be hereinafter identified, on the commutator brush support assembly 68 are in wiping engagement with the conductors printed upon the commutator 88.

The tiring contacts of the FIGURE 8 are identified as 178 and 180 which are oppositely disposed upon the support assembly 68 and joined by a printed conductor 182. Although both the tiring contacts 178 and 180 are electrically hot when detonation is desired, only one contact of the pair of contacts 178 and 180 will engage conductors coupled to the explosive charges or piston actuators 110. It will be noted that the contacts 178 and 180 as Well as the remaining contacts of the circuit are bifurcated so that a redundancy of contacts is provided so as to assure detonation of the piston actuators upon command. A Zero degree position contact 184 is positioned upon the support assembly 68 and a 180 position contact 186 is disposed approximately 180 from the 0 position contact 184. The function of the contacts 184 and 186 is to provide a signal indicating which pair of piston actuators 118 are in position for detonation. The ground contacts are indicated at 70 and 72 while the remaining contacts 188:1 through 188]' serve as grounding contacts for grounding out the non-selected piston actuators 110. When the selected piston actuators 110 are to be detonated, the conductors of the commutator 88 are so positioned so as to remove the selected piston actuators 110 from ground and position either the tiring contacts 178 or 180 upon their leads so as to be detonated upon command.

The commutator 88 of the FIGURE 9 is made up of a circular insulator 190, such as a phenolic resin, having a central aperture 192. Deposited upon the insulator 190, are a plurality of conductors of the deposited printed circuit type for performing the functions set forth as the commutator 88 rotates due to its connection to the piston lactuator housing 84. More specifically, a generally circular conductor 194 is deposited upon the insulator 190 and includes a plurality of short projections 196 which project into the insulator 190 and longer conductors 198 that extend into the central portion of the insulator 190 and form a ring 200 about the aperture 192. symmetrically disposed about the ring conductor 200 are a plurality of T shaped conductors 202a through 202k which are adapted to engage either one of the ground contacts 188a through 188] or the tiring contacts 178 or 180 of the FIGURE 8. Two of the piston actuators 110 are Ishown symbolically within the aperture 192 of the FIGURE 9 and are connected between the ring conductor 200 at ground potential and one of the conductors 202a through 202k. The conductors 202a through 202k remain `at ground potential unless `their associated piston actuator 110 has been selected for detonation. In this event, the rotation of the commutator 88 will cause o-ne of the conductors 202a through 202k to be removed from ground due to the positioning of the contacts 188g through 188k of the FIGURE 8 and the piston actuator 110 associated with the particular conductor 202a through 202k which has been selected for tiring, will now be tired or detonated upon receipt of a signal to the apparatus.

The functioning of the commutator brush support assembly 68 of the FIGURE 8 and the commutator 88 of the FIGURE 9 is shown symbolically in the FIGURE l0. Since a redundancy is provided with the piston actuators 110, a pair of piston actuators is shown in the FIG- URE 10 wherein one conductor 216 of each of the actuators 110 is connected to the ground conductor 194. The other conductor of each of the piston actuators 110 is indicated at 204 and is, when not in firing position, shorted to ground by one of the contacts 188:1 through 188]'. In addition, a conductor 206 is coupled between a pair of contacts 184 and 186 and oscillates between the two contacts so as to indicate whether the piston actuator housing 84 is in the 0 tiring position or the 180 firing position. Detonation or ring current is supplied on the contacts 178 or 180 and as shown in the FIGURE l0, the conductors 204 is always at ground potential unless the conductor 204 is that conductor associated with the selected piston actuators 110 to be detonated. In that event, the conductor 204 moves upwardly to engage one of the tiring contacts 178 or 180.

With reference to the FIGURE 11, the circuit provides a means whereby an indication may be derived as i to whether the magnetic flux sensor 158 is in its lirst position which may be termed 0 or in its second position which is 180 removed from its first position. The position of the sensing switches 80 and 82 and the eccentrically mounted pin 74 of the shaft 36 which engages the arms 76 and 78 extending from the switches 80 and 82, respective- 1y, are partially visible in the FIGURE 2. immediately to the right of the commutator brush support assembly 68. Again, with reference to the FIGURE 11, as the shaft 36 is indexed, the eccentrically mounted pin 74 will engage the extending arm 76 or 78 on one of the switches 80 or 82 and thus close :a circuit to provide an indication of the position of the magnetic iiux sensor 158. In the illustration of the FIGURE l1, the pin 74 is shown engaging the switch arm 76 of the switch 80 and has closed its contacts so that it produces an indication on a pair of terminals 208 that the magnetic fiux sensor 168 is in its first or 0 position. It will be readily understood that the use of the term first position and 0 is arbitrarily and is used only to provide an indication of the relative position of the magnetic flux sensor 158. In the event that three or more positions of the magnetic flux sensor 158 are desired, the apparatus would be modiiied accordingly and would thus provide three or more indications ofthe relative position of the magnetic flux sensor 158.

After another set of pistou actuators 110 are detonated, the shaft 36 will rotate approximately 180 and cause the eccentrically mounted pin 74 to open the switch 80 contacts by disengaging the switch arm 76 and will now engage the switch arm 78 of the switch 82 and close the contacts associated with that switch. Accordingly, on a pair of terminals 210, an indication may be derived as to the present position of the magnetic iiux sensor 158.

The FIGURE 12 illustrates the manner in which the piston actuator 110 engages one of the piston actuator surfaces 148 or 150 to step the device. Each piston actuator 110 includes an outer cylindrical casing 212. Within the casing 212 is an explosive charge 218 which is detonated by a current supplied to a small heater or detonator by the conductors 204, 216, and a movable piston 214 shown in dotted outline. Upon detonation, the piston 214' in solid outline, is driven outwardly to engage the piston impact surface 148 of the piston ratchet arm 134, thus rocking the piston ratchet arm 134 and the sensor ratchet arm 122 about the pin 140.

Operation Although the operation of the apparatus has previously been set forth, it is believed appropriate to briefly review the indexing apparatus and its functioning as an entity.

Initially, the apparatus will be assembled as shown in the FIGURES l and 2. Although the invention has been set forth with reference to the manner of positioning a magnetic iiux sensor 158, it will be readily evident that the sensor can take many other and varied forms without departing from the spirit and essential characteristics of the invention. The magnetic flux sensor 158 may be encapsulated in a suitable resin, as found convenient. A su'icient amount of liexible electrical cable is threaded from the electrical connector 22, about the cable conduit 34 and into the cable container 156 so as to permit a number of revolutions of the magnetic iiux sensor 158 commensurate with the number of piston actuators or explosive charges 110 carried aboard the indexing device.

With the cover 166 removed, a piston actuator 110 is positioned in each of the apertures 108 of the piston actuator housing 84. At the same time, the power spring 98 is placed under tension so as to bias the power spring housing and the piston actuator housing 84 in one direction while biasing the main shaft 36, the ratchet 112, the cable container 156 and the magnetic iiux sensor 158 in the opposite direction. Manipulation of the escapement movement will permit this operation.

With the electrical cables and conductors in place, a piston actuator in each of the apertures 108, and the power spring 98 under tension, the cover 166 is now placed over the indexing device and secured. The enti-re apparatus is now ready to perform its mission of measuring values of magnetic lields in outer space. `More specifically, the non-magnetic, explosive actuated indexing device of the present invention willv supply precision rotary motion on command for a system that requires only a limited number of operations and where electrical power is at a premium. The specific application of the indexing device of the present invention is to rotate a single magnetic liux sensor each time calibration of the instrument is desired. Such reversa-l of the axis of the magnetic flux sensor 158 is the only way absolute values of magnetic fields can be obtained from certain types of magnetometers such as employed in the present invention.

When rotation of the magnetic iiux sensor 158 is required, a signal will be transmitted to the apparatus which applies a short pulse of firing current to the contacts 178 and 180 and the conductor 182 therebetween (see FIG- URE 8). The commutator 88, best shown in the FIGURE 9, will be so positioned that the firing current on the aforementioned contacts will be applied to one of the conductors 20211 through 202k that is associated with the pair of piston actuators 110 immediately below one of the piston impact surfaces 148 or 150. For the purposes of explanation, we will `assume that the piston 148 is resting against the periphery of the piston actuator housing 84 as shown in the FIGURE 4. Symbolically, the conductor 204 ofthe FIGURE 10 would be moved upwardly against the contact designated Fire which corresponds with the contacts 178 or 180. As the piston actuators 110 immediately under the piston 148 of the piston ratchet 4arm 134 are detonated (see the FIGURE 12, also) the piston ratchet arm 134 of the FIGURE 4 would be pivoted in the direction of the arrow and since -the piston ratchet arm 134 is coupled to the sensor ratchet arm 122 by the pins 146 and 146 the sensor ratchet arm 122 would also be carried outwardly so as to disengage the hook 116 of the ratchet 112 from the stop 118 of the sensor ratchet arm 122. Also, the dog 142 of the piston ratchet arm 134 would disengage the pin 96a.

At this instant, the apparatus very quickly assumes its next stable position which is, for the magnetic iiux sensor 158, a position approximately 180 removed from its immediate former position, and for the piston actuator housing 84, a position so as to locate un-detonated piston actuators 110 under the piston impact surface 150 of the piston ratchet arm 134.

The foregoing is accomplished and is succinctly set forth in the FIGURES 5 and 7. The dog 144 rocks inwardly so as to engage the pin 96C and thus halt the clockwise rotation of the piston actuator housing 84. Undetonated piston actuators 110 are now positioned under the piston impact surface 150 for subsequent detonation when reorientation of the magnetic iiux sensor 158 is desired. Also, the hook 116 of the ratchet 112 has rotated approximately 180 under the urging of the power spring 98 so that the hook 116 now engages the stop 120 of the sensor ratchet a-rm 122. In the event that three or more stable positions of the sensing instrument are desired, it will be evident to those skilled in the art that the sensor ratchet arm 122 could be modified accordingly to provide three or more stops such as the stops 118 and 120.

As the piston actuator housing `84 rotates, it carries along with it the commutator 88 so that one of the firing contacts 178 or 180 are now in engagement with one of the conductors 202:1 through 202k which are electrically connected to the next set of piston lactuators 110 to be detonated. During the indexing of the commutator 88, the wipers or contacts 188a through 188]' cause all piston actuators 110 not selected for detonation to be placed at ground potential. In this manner, only the selected piston actuators 110 are detonated and positive action is thereby accomplished. Further, it will be noted that the piston actuators 110 are fired in `groups of two so that a red-undancy is present in the `event one of the piston actuators 110 should fail to fire. That is to say, the device will be indexed if only one piston actuator 111B should detonate and the second piston actuator 11) is provided as a back-up feature since statistically, two piston actuators 110 would rarely fail to fire upon command.

Signals are now available from conductors coupledto the contact 184 or 186 indicating from which side of the piston 'actuator housing 84 the next detonation will take place. In addition, the position of the magnetic flux sensor 158 would be indicated on one of the pair of terminals 208 or 210 ras shown in the FIGURE l1.

Thus, there has been described and illustrated a nonmagnetic indexing device for measuring minute magnetic fields. The conventional manner for indexing a shaft coupled to a magnetic fiux sensor is to employ a stepper motor or a solenoid actuated device. However, both of these methods, due to current flow, produce a magnetic field which cannot be tolerated since the magnitude of the generated magnetic fields may approach or exceed or interfere with the measurement of the unknown magnetic field. Accordingly, the primary advantage of the indexing device of the present invention is that it is completely non-magnetic but achieves its mission of determining absolute values of unknown magnetic fields such as those found around the earth and in distant space.

A particular novel feature of the present invention is the manner in which the explosive devices or piston actuators are incorporated to obtain repeated operations. Normally, such devices are only used for one-shot operations because, by their very nature, they can only be detonated once and cannot be retracted. However, the present invention has overcome these deficiencies and the present mechanism provides for the removal and replenishment of the explosive actuator for additional cycles of operation.

It will be evident to those skilled in the art that many modifications of the invention are evident. There are a number of different ways of obtaining the same mechanical output from the system of the present invention. For example, the dual -ratchet -arms can be replaced by a single ratchet arm and a gear train to couple the flux sensor and the piston actuator housing. In addition, a device incorporating a Aplanetary gear system has also been successfully constructed and operated in accordance With the principles of the present invention.

Thus, the present invention may be embodied in other specific forms Without departing from the spirit and the essential characteristics of the invention. The present embodiment is, therefore, to be considered in all respects as illustrative and the scope of the invention being indicated by the appended claims rather than the foregoing description, and all changes which come within the meaning and range of the equivalency of the claims are, therefore, intended to be embraced therein.

What is claimed is:

1. An indexing device comprising positionable means having at least -a first stable position and a second stable position, a rotatable ratchet coupled to said positionable means and having an engaging surface, an arcuate ratchet arm having at least two mating surfaces for retaining said ratchet in a stable position by engaging said surface, and explosive means for actuating said ratchet arm to release said ratchet from a mating surface for subsequent engagement with another mating surface.

2. An indexing device comprising positionable means having at least a first stable position and a second stable position, a rotatable pawl coupled to said positionable means, a pivotable, arcuate ratchet arm having pawl engaging surfaces equal in number to the number of stable positions of said positionable means, and explosive means for pivoting said ratchet arm to release said pawl at a pawl engaging surface to thereafter reengage said pawl at another pawl engaging surface.

3. An indexing device comprising positionable means having at least a first stable position and a second stable position, a rotatable pawl coupled to said positionable means, a first pivotable, ratchet arm having pawl engaging surfaces equal in number to the number of stable positions to said positionable means; a second pivotable ratchet arm coupled to said first ratchet arm, and explosive means for actuating said second ratchet arm to thereby pivot said first ratchet arm and release said pawl at a pawl engaging surface to thereafter re-engage said pawl at another pawl engaging surface.

4. The combination as defined in claim 3 including means for resiliently maintaining said first and second ratchet arms in a stable position after actuation by said explosive means.

5. An indexing device comprising positionable means having at least a first stable position and a second stable position, a rotatable pawl coupled to said positionable means, a first pivotable, arcuate ratchet arm having pawl engaging surfaces equal in number to the number of stable positions of said positionable means, a second pivotable, arcuate, ratchet arm coupled to said first ratchet arm, a circular housing means positioned within said second ratchet ann, and explosive means positioned within said housing means for causing expanding gases to actuate said second ratchet arm to thereby pivot said first ratchet arm and release said pawl at a pawl engaging surface to thereafter re-engage said pawl at another pawl engaging surface.

6. The combination as defined in claim including means for detonating said explosive means.

7. The combination as defined in claim 5 wherein said housing means includes a plurality of peripheral apertures for receiving a plurality of explosive charges.

8. The combination as defined in claim 7 including means for detonating selected explosive charges and means to index said housing means and thereby expose undetonated charges to said second ratchet means.

9. The combination as defined in claim 7 including means for urging said positionable means in one direction to its stable positions and for urging said housing means bearing explosive charges in the opposite direction.

10. The combination as defined in claim 9 wherein said means is a power spring having one end coupled for urging said positionable means and its other end for urging said housing means.

11. The combination as defined in claim 9 including means on said second ratchet and cooperating with said housing means for defining a plurality of indexable positions of said housing means, each indexable position corresponding to the position of an unused explosive charge.

12. Apparatus for positioning a sensing device alternately from a first position to a second position approximately 180 removed from the first position comprising a shaft for mounting said device, a ratchet secured to said shaft, a first ratchet arm for engaging said ratchet to thereby halt said device in its first and second positions, a housing loosely mounted about said shaft and bearing a plurality of equally spaced peripheral apertures, an explosive charge positioned in each of said apertures, a second ratchet arm coupled to said first arm and having a pair of inner surfaces displaced approximately 180 from each other for receiving the force exerted upon detonation of one of said explosive charges, means for biasing said housing in one direction and said shaft in the opposite direction, and means on said second ratchet arm and cooperating with means on said housing for indexing said housing so as to present an un-detonated charge under said inner surfaces of said second ratchet arm.

13. The combination as defined in claim 12 wherein said means for biasing is a coil spring and further includes 'a spring housing coupled to and enclosing an end of said spring, said spring housing ybeing secured to said housing loosely mounted about said shaft.

14. The combination as defined in claim 12 wherein said lratchets pivot and oscillate between a first position wherein one of said inner surfaces is next to an explosive charge and said other inner surface is removed from a charge and a second position wherein the position of said inner surfaces are reversed.

15. The combination as defined in claim 14 wherein the charge in said housing nearest one of said inner surfaces is designated the next charge to be detonated .and includingmeans for detonating said charge upon command so as to advance said sensing device in its next position.

16. The combination as defined in claim 14 including means for inhibiting the accidental firing of all charges except the selected charge.

17. The combination as defined in claim 14 wherein said means is a commutator `brush assembly cooperating with electrical conductors coupled to said charges.

18. The combination as defined in claim 12 including a second group of equally spaced apertures in said housing, said apertures arranged in pairs and housing a redundant explosive charge.

19. The combination as defined in claim 12 including means for detecting whether the sensing device is in its first position or its second position.

20. The combination as defined in claim 19 wherein said means includes an arm for engaging a iirst switch to indicate the first position and a second switch for indicating the second position.

21. Apparatus for positioning .a magnetic iiux sensor alternately from a first position to a second position approximately removed from the first position comprising generally arcuate supporting means, a shaft projecting int-o said supporting means and coupled to said flux sensor, a pawl secured to said shaft, a first ratchet arm pivoted from said supporting means for engaging said pawl to thereby halt said sensor in its first and second positions, a rotatable housing loosely mounted about said shaft and within said supporting means, a plurality of equally spaced peripheral apertures formed in said housing and directed toward said shaft, an explosive charge positioned in each of said apertures, a second ratchet arm coupled to said first arm and pivoted from said supporting means adjacent said charge supporting housing, 'a pair of piston surfaces formed on the inner surfaces Iof said second arm approximately 180 removed from each other and adapted to be actuated by the detonation of an explosive charge positioned thereunder, a commutator carried by said housing and bearing electrical conductors for coupling to said explosive charges, means on said second arm and said housing for indexing said housing after each detonation to thereby expose an undetonated charge to one of said piston surfaces, a coil spring for biasing said housing in one zdirection and said shaft and sensor in the opposite direction, and means for detonating the explosive charge under a piston surface to thereby Ipivot said second larm and index said housing to expose undetonated charges to a piston surface, an-d pivot said first arm to thereby momentarily -release said panel and permit said sensor to advance to its oth position. 2'

22. The combination as defined in claim 21 including means for indicating which position of the first and second positions that said sensor is residing.

23. The combination as defined in claim 21 including means onr said commutator for preventing the accidental detonation of unselected charges.

24. Shaft indexing lapparatus comprising a pawl coupled lto said shaft, a ratchet arm for engaging said pawl and having one or more pawl arresting positions, means for biasing said shaft toward a direction of rotation, a rotatabley housing loosely mounted upon said shaft and bearing a plu-rality of shaft oriented, peripheral apertures, an explosive charge positioned in each aperture, and means for detonating said explosive charge to thereby rock said arm to release said pawl t-o index said shaft to a new position.

25. Shaft indexing lapparatus comprising a pawl coupled to said shaft, a ratchet .arm for engaging said pawl and having one or more pawl arresting positions, means for biasing said shaft toward a direction of rotation, .a rotatable housing loosely mounted upon said shaft and bearing a plurality of shaft oriented, peripheral apertures, an explosive charge positioned in each aperture, a piston actuator arm connected to said ratchet arm and having piston surfaces positioned over selected ones of said exmeans for preventing the accidental detonation of uuselected charges.

References Cited UNITED STATES PATENTS 2,821,116 1/1958 Schwager et al 89--1 3,017,807 1/1962 Grouer 89-12 SAMUEL W. ENGLE, Primary Examiner. 

3. AN INDEXING DEVICE COMPRISING POSITIONABLE MEANS HAVING AT LEAST A FIRST STABLE POSITION AND A SECOND STABLE POSITION, A ROTATABLE PAWL COUPLED TO SAID POSITIONABLE MEANS, A FIRST PIVOTABLE, RATCHET ARM HAVING PAWL ENGAGING SURFACES EQUAL IN NUMBER TO THE NUMBER OF STABLE POSITIONS TO SAID POSITIONABLE MEANS; A SECOND PIVOTABLE RATCHET ARM COUPLED TO SAID FIRST RATCHET ARM, AND EXPLOSIVE MEANS FOR ACTUATING SAID SECOND RATCHET ARM TO THEREBY PIVOT SAID FIRST RATCHET ARM AND RELEASE SAID PAWL AT A PAWL ENGAGING SURFACE TO THEREAFTER RE-ENGAGE SAID PAWL AT ANOTHER PAWL ENGAGING SURFACE. 